The other thread where you replied ( Raspberry Pico based motor stage - Contributions - OpenFlexure Forum) has a port for Pico from a contributor. We are still working on getting the instructions for a Pico work-around with supported firmware.
The answer to a standard motor control is the Sangaboard V0.5, which is custom but is available, or the Nano-workaround. The work-arounds offered do assume more affinity with building things, and are not proscriptive because people want to work around elements of the workaround.
Just to note, the Arduino Nano (and Sangaboard V0.3 which uses the same microcontroller) are perfectly capable as the motor controller. The change to RP2040 (the Pico micorcontroller) for Sangaboard V0.5 is partly (or mainly) about cost and availability of the part. Also I think ease of implementation on a custom board, and then it also offers more flexibility in GPIO to add functions beyond a 3-axis motor driver. Cheap Arduino Nano clones will do everything the microscope actually needs.